1. Field of the Invention
This invention pertains generally to electromechanical and high-throughput sensors and more particularly to chitin or chitosan functionalized cantilever-based sensors for infrared detection, imaging and low cost ambient temperature sensor arrays.
2. Description of Related Art
For many years, cantilever structures have been used in microelectromechanical systems (MEMS) as simple sensor elements for transducing environmental stimuli. MEMS cantilevers are typically fabricated from silicon, silicon nitride or polymer materials and can be produced on very small scales through conventional etching techniques.
MEMS cantilevers have been used for biodetection devices, where an analyte binds to an agent on the cantilever surface and the mass of the combination causes the cantilever beam to deflect. These structures have also found application in optical, infrared and thermal detection, where incident energy is absorbed and through a mismatch in thermal properties causes the beam of the cantilever to deflect. One of the primary challenges in using cantilevers for sensing is the need to maximize the sensitivity of the device. Sensitivity is dependent on the geometry of the cantilever beam, the choice of materials, and the quality of the energy coupling.
The method of readout for cantilever-based sensors is also a significant challenge in the development of integrated sensors, imaging arrays and high-throughput systems. Since each element needs to be addressable, the readout generally requires either an optical setup or a custom circuit to be attached to each cantilever. The optical approach generally makes use of large, expensive, and mostly detached (or remote) equipment, to input and measure the amount of light and the specific wavelength(s) that are returned. For example, in atomic force microscopy, laser light is reflected off of the cantilever holding the probe tip, and its reflected position is used to determine the amount of deflection in the cantilever beam.
The circuit approach is normally used to perform piezoresistive or capacitive measurements, and must be integrated with each cantilever device, and may make use of multiplexers to share a readout circuit across multiple devices. MEMS strain gauges, for example, typically rely on the material property of piezoresistivity in order to transduce a strain in the cantilever into a change in resistance. Subsequent electrical circuitry, such as a Wheatstone bridge, may be used to convert the resistance change into a voltage. The challenge with the circuit approach is integration with the MEMS fabrication process and interfacing into an array. In many applications, an array of cantilever elements allows for high-throughput or 2D (focal plane array) imaging.
Infrared sensors have many medical, military, industrial and commercial applications. These IR sensors generally fall within two categories—photonic and thermal. Photonic IR sensors have very narrow bands and require cryocooling for operation that results in high power consumption and very large bulk. Thermal detectors form a class of infrared detectors, including pyroelectrics, bolometers, thermistors, thermopiles and Golay cells, and are generally uncooled. However, both microbolometers and pyroelectrics are electro-resistive devices and are therefore still quite sensitive to thermal noise resulting in lower sensitivities and resolutions compared to cryocooled photonic IR sensors. Low temperature requirements often make many existing infrared detector designs unsuitable for ambient temperature applications.
Accordingly, there is a need for an inexpensive apparatus and system that is responsive to infrared radiation at various wavelengths at ambient temperatures and can be adapted to many different sensor needs. The present invention satisfies this need as well as others and is a general improvement over the art.